ZB : a tool suite for real-time wireless networked applications

IEEE 802.15.4/ZigBee and TinyOS have been playing an important role in leveraging a new generation of largescale networked embedded systems. However, based on previous experience on the implementation and use of the IEEE 802.15.4/ZigBee protocols over TinyOS, several problems (producing loss of synchronization and even network crashes) emerge due to some limitations of TinyOS, namely related to the lack of task pre-emption and prioritization. This unreliability is not a major concern for non-critical environments where the device nodes are supposed to guarantee best effort services. However when real-time guarantees are required, different software solutions must be used to support real-time services in such networked applications. This being our objective, we implemented the IEEE 802.15.4 protocol over ERIKA, a real-time operating system for resource-constrained embedded systems. The results at tained so far, and reported in this paper, demonstrate that ERIKA enables reliable network behaviour and improved network performance. This paper presents the most important aspects of the software implementation and reports comparative experimental results based on real hardware and software platforms. We show that the implementation of the Open-ZB protocol on ERIKA outperforms the TinyOS implementation. Thus, we demonstrate that it is indeed possible to use WSNs in demanding applications, by guaranteeing at the same time high throughput and real-time behaviour.